I know its quite on old topic now, but I thought that since I found a solution,
I might just confirm it, so it may help in future.
c beck,Your suggestion "/boot/vmlinuz-2.6.32.-generic?" worked. It needed a full
path to the header. I dont understand why though. For future reference, however,
I would recommend that copy grub menuentry contents from the grub.cfg file and
paste into your custom file, and then you can edit your custom file as per your
wishes.
Hope it was useful. And thank you for your sharing your ideas.